Abstract To provide an effective support device for dealing with the instability problems in geotechnical engineering, this paper proposes a new energy-absorbing rock bolt based on the existing energy-absorbing devices, called compression-expansion-friction bolt (abbreviated as the CEF bolt). The CEF bolt mainly consists of two parts, a variable-diameter tube and a hollow cone attached at the distal end of the bar. Controllable constant resistance and large displacement are the characteristics of the CEF bolt. The constant resistance was generated by the expansion of the tube under the compression of the cone, as well as the friction between the tube and cone. And the large displacement was provided by the sliding of the cone relative to the tube. A theoretical model was developed to predict the constant resistance by taking into account the effect of material strain-hardening. Based on the energy conservation law, the effect of shear deformation was also considered. Further, the current model was formulated as three forms to consider different conditions. The predictions of the current theoretical model were in good agreement with existing experimental data. An experimentally validated finite element model was established to study the effects of main parameters on the constant resistance of the CEF bolt, such as cone angle, tube wall thickness, friction coefficient, expansion ratio and the strain-hardening property of the tube. The results of numerical simulation and theoretical analysis show that the constant resistance was directly proportional to the tube wall thickness, friction coefficient, expansion ratio and the strain-hardening modulus of the tube. But the constant resistance increased first and then decreased with respect to the cone angle, with an inflection point existed between 5° and 10°. The shear stress distribution and the deformation of the tube were investigated as well. According to the shear stress distribution, the zone under expasion of the tube can be divided into three characteristic areas: stress concentration area, smooth transition area, and stress re-concentration area. In addition, compared with the large number of experimentally validated numerical results, the wide applicability and sufficient accuracy of the current theoretical model were verified. By taking the derivative of the current theoretical model, the location of the inflection point can be obtained. These results can provide theoretical basis for the design and field application of the CEF bolt, as well as the similar structure.

中文翻译：

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一种新型恒阻大位移吸能锚杆的理论与数值分析

摘要 为解决岩土工程中的失稳问题提供有效的支撑装置，本文在现有吸能装置的基础上，提出一种新型吸能岩石锚杆，称为压胀摩擦锚杆（简称CEF锚杆）。 . CEF螺栓主要由两部分组成，可变直径管和连接在杆远端的空心锥。可控恒阻和大位移是CEF螺栓的特点。恒定阻力是由管子在锥体压缩下的膨胀以及管子与锥体之间的摩擦产生的。大位移是由锥体相对于管子的滑动提供的。通过考虑材料应变硬化的影响，开发了一个理论模型来预测恒定电阻。基于能量守恒定律，还考虑了剪切变形的影响。此外，当前模型被制定为三种形式以考虑不同的条件。当前理论模型的预测与现有的实验数据非常吻合。建立了经实验验证的有限元模型，研究了锥角、管壁厚度、摩擦系数、膨胀比和管的应变硬化性能等主要参数对CEF螺栓恒定阻力的影响。数值模拟和理论分析结果表明，恒阻与管壁厚度成正比，管的摩擦系数、膨胀比和应变硬化模量。但恒定电阻相对于锥角先增大后减小，拐点存在于5°和10°之间。还研究了管的剪切应力分布和变形。根据剪应力分布，管材受胀区可分为三个特征区：应力集中区、平滑过渡区和应力再集中区。此外，与大量实验验证的数值结果相比，验证了当前理论模型的广泛适用性和足够的精度。通过对当前理论模型的导数，可以得到拐点的位置。